"OpenCV manager was not found" error on device

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The only thing that my code is difference with the other samples is that I used TabHost for main activity. I mean isn't that exactly why it doesn't run? Couldn't you start from a sample that works and merge your code in there?

I confirmed that it works when OpenCV is used in the main activity. But it doesn't work when it used in the TabHost. I called the class as intent like this. OpenCV is imported in "LFSize.class". The error is occurred when I open the tab.

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    final TabHost tabHost = getTabHost();

    Intent int1 = new Intent(this, com.example.automqa.LFSize.class);
    int1.addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP);
    tabHost.addTab(tabHost.newTabSpec("tab1")
            .setIndicator("Light Field Size")
            .setContent(int1));
    }